Work string tubulars enable drilling engineers to access a wellbore after a well casing has been cemented and/or fracked. The construction of work string tubes is different from that of drill pipe in that the box and pin are integral upset regions within the tube itself. Drill pipe construction incorporates forged tool joints welded to a tube (see FIG. 1). Work string tubes are integrally formed tube members that are typically 2⅜″ and 2⅞″ in diameter and 30′ long; however, other sizes tubes can be used (see FIG. 1). The work string tubes are generally formed of high strength metal such as P110 (0.26-0.35% C, 0.17-0.37% Si, 0.4-0.7% Mn, ≤0.02% P, ≤0.01% S, 0.8-1.1% Cr, ≤0.2% Ni, ≤0.2% Cu, 0.15-0.25% Mn, ≤0.08% V, ≤0.02% Al, bal. Fe), a widely used grade tube having various thread connections with a yield strength of about 110,000 psi, or PH6™ metal (a proprietary Hydril® connection). Work string tubes generally have a thinner metal thickness than standard drill pipe; thus, when work string tubes encounter excessive wear, the rehabilitation of the work string tubes is generally considered too difficult and worn work string tubes are generally discarded.
During a typical work string operation, the work string tube connections' outside diameter is subjected to considerable wear. In work string operations, the use of the work string tube is terminated when the upset outer diameter and inner diameter (i.e., upset wall thickness) calculates to less than an acceptable percent of the OEM torsional capacity for any specific type of work string tube. Generally, when the upset outer diameter and inner diameter calculates to less than 80% of the OEM torsional capacity for any specific type of work string tube, the work string tube is deemed unacceptable for further use in wellhole operations; however, for different operations and types of work string tubes, the value can be higher or lower than 80%. The tube body, however, which does not wear at the same rate as the upset connections, is typically still within specification and can typically be further used. However, because the connections between the work string tubes have been worn to less than acceptable use standards, the work string tube is downgraded to less than premium grade and is, therefore, unusable for further service in work string operations. Because of the severe wear of the tubing connection upset area, many work string tubes lay dormant in pipe yards throughout the oilfield country. The upset areas of the work string tubes are normally considered non-weldable because the welding arc used during a typically hardfacing operation generally penetrates through the thin wall of the work string tube and/or damages the threading in the box of the work string tube and renders the work string tube useless.
“Hardfacing” is an arc welding technique which involves applying a layer of hard material to a substrate for the purpose of increasing the wear and corrosion resistance of the substrate. The use of this technique has increased significantly over the recent years as the oil and gas industries have come to recognize that the substrates of softer, lower cost material can be hardfaced to have the same wear and corrosion resistance characteristics as the more expensive substrates of a harder material. Additionally, some existing substrates that have been rendered useless in the industry can be hardfaced to restore and/or improve the wear and abrasion characteristics of the original substrates.
Hardfacing involves the deposition of a hard layer by arc welding or thermal spraying. Conventional weld hardfacing is accomplished by oxyfuel welding (OFW), gas tungsten arc welding (GTA), gas metal arc welding (GMAW), shielded metal arc welding (SMAW) and flux-cored arc welding (FCAW). Plasma transferred arc (PTA) hardfacing and laser beam hardfacing can also be used.
In view of the prior art, there remains a need for a process which can circumvent the problems associated with hardfacing of the thin upset areas of the pin and box connections of work string tubing so that used work string tubing can be reused.